The present invention relates to a resistor film for constituting a resistor to be used in various electronic parts such as hybrid ICs, thermal heads, and the like, and a method for forming such a resistor film. In particular, the invention relates to a resistor film formed by using thick-film technique, and a method for forming the same.
The technique for forming a resistor film is classified into two, namely, thick-film technique and thin-film technique. The thin-film technique is a technique for forming a resistor film on a surface of an insulating substrate in a vacuum container by means of vapor deposition, sputtering, or the like. The thin-film technique has an advantage in that a thin and uniform resistor film can be formed, but it has a problem in that a large-scaled production equipment to bring about an increase in cost is required.
The thick-film technique is a technique for forming a resistor film by applying or printing a resistor-forming paste or solution on a surface of an insulating substrate and drying and burning it. The thick-film technique has an advantage in that low equipment cost and high production efficiency can be attained However, the resistor film formed by using the conventional thick-film technique is, in general, thick. There arises a problem in that the heat capacity of the resistor film is large Further, the resistor film is formed of a sintered matter of powder having a particle size of the order of .mu.m. Accordingly, there arises a problem in that the resistance value of the resistor film varies widely Consequently, there arises a problem in that a thermal head using the resistor film as a heating resistor is large in the quantity of energy consumption and is inferior in thermal response.
Heretofore, various techniques for producing a thin-film-like resistor film by using the aforementioned thick-film technique being low in the cost of the equipment have been proposed.
For example, Japanese Patent Unexamined Publication No. Sho-64-54710 has described a method for forming a thin-film-like resistor film containing a perovskite type ruthenate monolayer formed by applying a mixture solution of ruthenium octylate and alkaline-earth metal octylate and burning the mixture solution.
The resistor film containing a perovskite type ruthenate monolayer, described in the Japanese Patent Unexamined Publication No. Sho-64-54710, that is, the resistor film having a perovskite type crystal structure of ruthenium, has excellent film-forming characteristics (uniformity of the produced resistor film (in which the resistor film has no crack and no unevenness and has uniform resistance values in respective portions thereof), close adhesion to the surface of the substrate, and the like) and excellent electric characteristics (characteristics in the change of the resistance value at the time of electric power supply). However, it is difficult to produce the resistor film having a perovskite type crystal structure. It is considered that the reason is in that used materials and process conditions such as burning conditions and the like are severely restricted in order to form the resistor film having a perovskite type crystal structure.
On the other hand, the applicant of the present application has invented a method for producing a thin-film-like resistor film by using the aforementioned thick-film technique being low in the cost of equipment, that is to say, a metallo-organic deposition (MOD) method, and has filed a patent application (Japanese Patent Application No. Sho-63-222931). According to the MOD method, the resistor film for forming a heating resistor or the like is formed by applying onto a substrate a homogeneous mixture solution of metal organic compounds including metals selected from the metal group of silicon (Si), bismuth (Bi), lead (Pb), aluminum (Al), zirconium (Zr), calcium (Ca), tin (Sn), boron (B), titanium (Ti), barium (Ba), and the like, and a metal selected from the metal group of iridium (Ir), ruthenium (Ru), rhodium (Rh), and the like, and burning the homogeneous mixture solution.
The structure in components of the resistor film formed by the MOD method varies according to the conditions, such as metal organic material used, burning temperature, burning time, and the like. In short, the components of the resistor film formed by the MOD method may form one or two kinds of crystal structures, or may form no crystal structure. As the structure in components of the resistor film varies, the film-forming characteristics and electric characteristics of the resistor film vary.